Process for treating Al alloy casting and die casting

Abstract

Aluminum alloy castings and aluminum alloy die castings are treated in the process comprising the steps of chemically polishing the castings, processing the chemically polished castings by barreling and/or by blasting and subjecting successively the castings to degreasing, anodic oxidation, dyeing and sealing.

We claim: 
     
       1. A process for treating an aluminum alloy casting or an aluminum alloy die casting, the process comprising the steps of chemically polishing the casting with a bath containing phosphoric acid, processing the chemically polished casting by tumbling and/or by blasting and subjecting successively the casting to degreasing, anodic oxidation, dyeing and sealing. 
     
     
       2. A process as defined in claim 1 wherein the chemical polishing is conducted in a bath containing about 40 to about 80% by weight of phosphoric acid and about 2 to about 10% by weight of nitric acid. 
     
     
       3. A process as defined in claim 1 or 2 wherein the chemical polishing bath further contains at least one of about 5 to about 30% by weight of sulfuric acid, about 5 to about 15% by weight of acetic acid and about 0.02 to about 0.05% by weight of copper nitrate. 
     
     
       4. A process as defined in one of claims 1 or 2 wherein the chemical polishing is carried out at a temperature of about 90° to about 120° C. for about 5 to about 300 seconds. 
     
     
       5. A process as defined in claim 1 wherein the degreasing is performed in a bath containing at least one of sulfuric acid, nitric acid, phosphoric acid and oxalic acid in a concentration of about 5 to about 35% by weight and/or a surfactant in a concentration of about 0.1 to about 1.5% by weight. 
     
     
       6. A process as defined in claim 1 or 2 wherein the degreasing is carried out at a temperature in the range of room temperature to about 100° C. for about 30 to about 400 seconds. 
     
     
       7. A process as defined in claim 1 wherein the anodic oxidation is conducted in a solution containing at least one of sulfuric acid, oxalix acid and like organic acids. 
     
     
       8. A process as defined in claim 7 wherein the solution contains about 5 to about 25% by weight of sulfuric acid and/or about 0.1 to about 1% by weight of oxalic acid. 
     
     
       9. A process as defined in one of claims 1, 7 or 8 wherein the anodic oxidation is conducted at a temperature of about 10° to about 30° C. and at a current density of about 1 to about 50 A/dm 2  for about 15 to 120 minutes. 
     
     
       10. A process as defined in claim 1 wherein the dyeing is carried out in a bath having a dye concentration of about 1 to about 15 g/l at a temperature ranging from room temperature to about 60° C. for about 10 seconds to about 20 minutes. 
     
     
       11. A process as defined in claim 1 wherein the sealing is effected in a solution containing about 1 to about 10 g/l of nickel acetate. 
     
     
       12. A process for treating an aluminum alloy casting or an aluminum alloy die casting, the process comprising the steps of chemically polishing the casting with a bath containing phosphoric acid, treating the chemically polished casting with a bath containing at least one of hydrofluoric acid and fluorine compounds, processing the treated casting by tumbling and/or by blasting and subjecting successively the casting to degreasing, anodic oxidation, dyeing and sealing. 
     
     
       13. A process as defined in claim 12 wherein the chemical polishing is conducted in a bath containing about 40 to about 80% by weight of phosphoric acid and about 2 to about 10% by weight of nitric acid. 
     
     
       14. A process as defined in claim 12 or 13 wherein the chemical polishing bath further contains at least one of about 5 to about 30% by weight of sulfuric acid, about 5 to 15% by weight of acetic acid and about 0.02 to about 0.05% by weight of copper nitrate. 
     
     
       15. A process as defined in claim 12 to 13 wherein the chemical polishing is carried out at a temperature of about 90 to about 120% for about 5 to about 300 seconds. 
     
     
       16. A process as defined in claim 12 wherein the bath containing hydrofluoric acid and/or fluorine compound has a fluorine ion concentration of about 1 to about 20%. 
     
     
       17. A process as defined in claim 12 or 16 wherein the bath further contains about 3 to about 40% of nitric acid and/or about 10 to about 30% of sulfuric acid. 
     
     
       18. A process as defined in claim 12 or 16 wherein the treatment of the chemically polished casting with the fluorine ion-containing bath is conducted at a temperature of about 0° to about 40° C. and for about 5 to about 180 seconds. 
     
     
       19. A process as defined in claim 12 wherein the degreasing is performed in a bath containing at least one of sulfuric acid, nitric acid, phosphoric acid and oxalic acid in a concentration of about 5 to about 35% by weight and/or a surfactant in a concentration of about 0.1 to about 1.5% by weight. 
     
     
       20. A process as defined in claim 12 or 19 wherein the degreasing is carried out at a temperature in the range of room temperature to about 100° C. for about 30 to about 400 seconds. 
     
     
       21. A process as defined in claim 12 wherein the anodic oxidation is conducted in a solution containing at least one of sulfuric acid, oxalic acid and like organic acids. 
     
     
       22. A process as defined in claim 21 wherein the solution contains about 5 to about 25% by weight of sulfuric acid and/or about 0.1 to about 1% by weight of oxalic acid. 
     
     
       23. A process as defined in one of claims 12, 21 and 22 wherein the anodic oxidation is conducted at a temperature of about 10° to about 30° C. and at a current density of about 1 to about 50 A/dm 2  for about 15 to 120 minutes. 
     
     
       24. A process as defined in claim 12 wherein the dyeing is carried out in a bath having a dye concentration of about 1 to about 15 g/l at a temperature ranging from room temperature to about 60° C. for about 10 seconds to about 20 minutes. 
     
     
       25. A process as defined in claim 12 wherein the sealing is effected in a solution containing about 1 to about 10 g/l of nickel acetate. 
     
     
       26. A process for treating an aluminum alloy casting or an aluminum alloy die casting, the process comprising the steps of chemically polishing the casting with a bath containing phosphoric acid, treating the chemically polished casting with a bath containing phosphoric acid, nitric acid, and at least one of hydrofluoric acid and fluorine compounds, processing the treated casting by tumbling and/or by blasting and subjecting successively the casting to degreasing, anodic oxidation, dyeing and sealing. 
     
     
       27. A process as defined in claim 26 wherein the chemical polishing is conducted in a bath containing about 40 to about 80% by weight of phosphoric acid and about 2 to about 10% by weight of nitric acid. 
     
     
       28. A process as defined in claim 26 or 27 wherein the chemical polishing bath further contains at least one of about 5 to about 30% by weight of sulfuric acid, about 5 to 15% by weight of acetic acid and about 0.02 to about 0.05% by weight of copper nitrate. 
     
     
       29. A process as defined in claim 26 or 27 wherein the chemical polishing is carried out at a temperature of about 90 to about 120% for about 5 to about 300 seconds. 
     
     
       30. A process as defined in claim 26 wherein the bath for treating the chemically polished casting contains fluorine ion in a concentration of about 2 to about 15%, phosphoric acid in a concentration of about 35 to about 75% and nitric acid in a concentration of about 2 to about 25%. 
     
     
       31. A process as defined in claim 26 wherein the treating of chemically polished casting is carried out at a temperature less than 40° C. for about 10 to about 180 seconds. 
     
     
       32. A process as defined in claim 31 wherein the treating is carried out at a temperature between about 15° to about 30° C. 
     
     
       33. A process as defined in claim 26 wherein the degreasing is performed in a bath containing at least one of sulfuric acid, nitric acid, phosphoric acid and oxalic acid in a concentration of about 5 to about 35% by weight and/or a surfactant in a concentration of about 0.1 to about 1.5% by weight. 
     
     
       34. A process as defined in one of claims 26 and 33 wherein the degreasing is carried out at a temperature in the range of room temperature to about 100° C. for about 30 to about 400 seconds. 
     
     
       35. A process as defined in claim 26 wherein the anodic oxidation is conducted in a solution containing at least one of sulfuric acid, oxalic acid and like organic acids. 
     
     
       36. A process as defined in claim 35 wherein the solution contains about 5 to about 25% by weight of sulfuric acid and/or about 0.1 to about 1% by weight of oxalic acid. 
     
     
       37. A process as defined in one of claims 26, 35 and 36 wherein the anodic oxidation is conducted at a temperature of about 10° to about 30° C. and at a current density of about 1 to about 50 A/dm 2  for about 15 to 120 minutes. 
     
     
       38. A process as defined in claim 26 wherein the dyeing is carried out in a bath having a dye concentration of about 1 to about 15 g/l at a temperature ranging from room temperature to about 60° C. for about 10 seconds to about 20 minutes. 
     
     
       39. A process as defined in claim 26 wherein the sealing is effected in a solution containing about 1 to about 10 g/l of nickel acetate.